vX: Function returns the principal value of the angle whose hyperbolic sine (expressed in radians) is vX. Function returns Null if vX is Null or cannot be fixed up to a real or complex number (as defined by the ComplexStringToReals function). Complex numbers are represented within strings as "R|I" where R is the real part and I is the imaginary part. Note: Microsoft named this function HArcsin within their Derived Math Function help topic.